Fig. 6

Enhanced canonical Wnt signaling is responsible for reduced cardiomyocyte numbers in kny/gpc4 mutants. (A-D) In situ hybridization for axin2 at the 15-somite stage. Dorsal views (A,C) of WT (A,B) and kny/gpc4 mutant (C,D). (B,D) Cross-sections through embryos stained for axin2 (blue) and nkx2.5 (orange) of WT (B) and kny/gpc4 mutant (C). Arrows indicate ectopic axin2 signal in anterior LPM. Dashed lines in A and C indicate location of the sections shown in B and D, respectively. (E) Timeline of rescue experiments with Tg(hsp70:dkk1-gfp, myl7:galFF/UAS:h2a-gfp). HS, heat shock; 14s, 14-somite. (F) Confocal image reconstruction of wild-type or kny/gpc4 mutant embryos with or without heat shock at 48hpf, stained for GFP (green) and Amhc (red). (G) Quantification of cardiomyocytes in corresponding embryos (n=3). Results are represented as mean±s.e.m. *Pd0.05, **Pd0.01. (H) Schematic of GPI-anchored Glypican4 protein with heparin sulphate chains that can sequester growth factors, such as Wnt and Bmp, in the ECM. (I) Model summarizing the major findings of this work.